The timing analysis of [1]} showed that this soft X-ray
component variability strongly correlates with the hard X-ray
variability on short timescales i.e. is driven by
reprocessing. However, on longer timescales, there is additional
variability in the soft X-ray flux, implying that there are intrinsic
fluctuations in the disc emission as well. The result that much of
the short term variability correlates with the hard X-rays rules out a
completely separate soft X-ray component such as the jet, while the
additional soft X-ray variability shows that the component is truly
separate as opposed to being produced from continuum curvature of the
X-ray emission or reflection (suggested by [2]} as a
potential origin for the soft X-rays). These variability constraints
mean that there are only two potential origins for the soft X-ray
component which arises from a small area with relatively high
temperature. Firstly, this could be emission from the surface of a
residual inner disc, forming a small ring from the last stable orbit
to some (small) outer radius. Secondly, this could be the inner face
of a truncated disc. We sketch these two possibilities in
Fig. REF , and outline them below.
